DNA samples were taken from 2,877 smokers in order to identify the occurrence of common single nucleotide polymorphisms, grouped into four haplotypes.

The researchers assessed the level of nicotine dependence for all smokers and recorded the age at which smoking began and the number of cigarettes smoked each day.

They found that people who began smoking before the age of 17 and possessed two copies of the high-risk haplotype for the nicotine receptors had from a 1.6-fold to 5-fold increased risk of heavy smoking as an adult.

For people who began smoking at the age of 17 or older, the presence of the high-risk haplotypes did not significantly influence their risk of later addiction.

The researchers, from the University of Utah and the University of Wisconsin, say that the study adds to recent advances showing how genetic variation can affect susceptibility to nicotine addiction.

sanjay.tanday@haymarket.com

PLOS Genetics Online 2008

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